This study will assess the role of chlamydial organisms, especially Chlamydia pneumoniae as well as other respiratory syndromes by studying the prevalence, clinical symptoms, and serological response of patients in various populations. Specimens from healthy children, university students, geriatric patients, and NIH immunocompromised patients will be studied. A one milliliter portion of all bronchial alveolar lavage (BAL) specimens that are submitted to the NIH microbiology service will be frozen at minus 70 degrees Centigrade and sent to the chlamydia laboratory at Johns Hopkins Hospital in Baltimore, Maryland for testing. Tests to be performed include culture, ELISA, PCR, and fluorescent antibody staining. Serum from these patients will also be sent to determine serological response to chlamydia. A clinical data form will be prepared from information obtained by chart review.